A compact high power ultrashort femtosecond fiber laser for high resolution second harmonic OCT This SBIR phase I project proposes a novel all-fiber and ultra compact high power mode locked fiber laser system by using our proprietary technologies on polarization shaping and pulse shaping. The proposed idea is an enabling technology for optical SH-OCT with its ultrashort fs pulses. The system proposed by PolarOnyx employs various types of photonics crystal fibers to manipulate the dispersion, SPM, XPM, and wavelength dependent polarization. Photonics crystal fiber is used in providing anomalous dispersion and dispersion compensation over a wide range of wavelength. It has no moving parts and requires less space. The cost and size will be at least ten times cheaper than other competing approaches. The design is simple in construction and easy to operate. In Phase I time frame, a prototype will be built up to demonstrate the functions of mode locking and high power amplification for fs pulses. Fine tuning of the product to achieve < 100 fs pulse width and > 1 W (average power) fiber laser will be given in Phase II with an investigation of volume production. APPLYING FOR NATIONAL INSTITUTE OF BIOMEDICAL IMAGING AND BIOENGINEERING (NIBIB) BIOIMAGING RESEARCH TOPIC B The proposed compact high power femtosecond fiber laser provide a breakthrough in applying femtosecond laser technology into real clinic. Though second harmonic OCT (SH-OCT) is our first application in obtaining high resolution image, it will have significant impact to other biomedical applications. [unreadable] [unreadable] [unreadable]